The present invention relates to gear-type fluid displacing machines, especially to external gear-type hydraulic pumps or motors, and, more particularly, to improvements in the sealing of the housing.
In presently known gear-type machines, high and lower pressure areas are generated within the chamber which houses the rotating gears. It is known to separate these areas from each other by using seals having round, rectangular or a square-shaped configuration. No matter which of these configurations is utilized in a particular application, opposite sides of these prior art seals are clamped and compressed between two parts of the housing.
Such seals present some very serious disadvantages which affect the output and efficiency of the machine. First of all, a considerable clamping force is generally required to provide an effective seal which is operative both under low and high loading conditions of the machine. Thus, the bearing members which engage one side of the seal are strongly urged against the gears so that, even under relatively low pressure conditions, undesirable wear of the gears results.
In addition, the seals of the prior art are generally constituted of rubber material so that after a period of use, it is common for the rubber material to flow away from the clamping portions of the housing. This evidently reduces the sealing effect since the prior art seals, which are originally clamped with an initial tightening force, need to be periodically retightened.